Spring mechanism on a clutch

ABSTRACT

A spring apparatus for a positive engagement clutch in which a sliding sleeve is forced into and out of locked engagement with a drive shaft by a spring mechanism. The spring mechanism includes a shift fork containing sliding blocks which engages with a peripheral groove on the sliding sleeve, a prestressing lever, and a spring guide. The spring guide interconnects the shift fork and the prestressing lever. The prestressing lever is capable of being locked in an engaged position in which the spring is compressed until the sliding sleeve engages with the drive shaft, and a disengaged position in which the spring is relaxed and a rigid connection occurs.

The invention is concerned with a spring mechanism for a positiveengagement clutch such as it has been disclosed in DE-C No. 29 49 149.In arrangements of this kind, the springs are usually integrated withthe sliding sleeve or the shift fork and therefore are not very easilyassembled. In another kind of assembly (according to DE-C No. 578 901),the springs are concentrically situated around the main axis of theshaft. In both cases the overall length of the springs adds to theoverall axial length of the clutch itself and thus requires more overalllength for the respective gearing. Moreover, after the assembly iscompleted, it is not possible to individually adjust the engaging forcesand feed paths by setscrews or the like. The adjusting force in thesolutions known already must also be maintained on the pivot shaft untileffecting or releasing the engagement. Also direct disengagement(without spring action) is not provided thereby so that the driver isnot given a feeling of assurance that complete disengagement hasoccurred.

The invention is directed to the problem of providing a spring mechanismfor positive engagement clutches which can be quickly and easilyengaged, simply assembled and readjusted, and with which the axialoverall length of the clutch is also less affected and a directspringless disengagement is possible.

The solution of the problem consists in that the springs are nowsupported outside, on the periphery of the sliding sleeve, between aprestressing lever and a shift fork by a spring guide bolt. Theexpansion of the spring allows the end portions of a bolt to abutagainst the external sides of the lever and the fork, but when pressureis exerted by the lever thereby compressing the spring against the shiftfork, the pressure is released only when the sliding sleeve is engaged.

Thus any additional axial overall length on the shaft, is prevented andthe springs remain outside the heating zone of the sliding sleeve.Assembly and adjustment of the spring mechanism is possible withoutdismounting the sliding sleeve, and several parts remain unchanged andthey can be used with different size sleeves, shifting forces and feedpaths. In addition, disengagement is directly possible with a positiveconnection of prestressing lever and shift fork via the end portions ofthe bolt. The springs also prevent transmission of vibration from thesliding sleeve to the pivot shaft or vice-versa, and end stops do notneed to be situated in the driver's compartment (mostly rubbercushioned) making allowances for other play-causing joints, etc. Thespring resistance increases only briefly upon actual engagement of thestop. The shift fork and the prestressing lever can be advantageouslymanufactured as sheet-metal molded parts at reasonable costs.

The following advantages are obtained.

The spring prestressing in the final positions of the sliding sleeve canbe reduced.

The actual actuation periods are limited to those needed for arriving atone of the stop positions.

A kinematically favorable arrangement results from a double use of thepivot shaft or the bearing thereof.

A favorable distribution of force onto the springs is obtained and adouble use therefor is achieved.

A lever and stop design favorable to mass production is obtained.

The invention is explained in detail with reference to the followingembodiments:

FIG. 1 shows a cross sectional view through the shaft and slidingsleeve, with the spring guides that engage the pivot ends of the shiftfork, and the support of the prestressing lever on the pivot shaft of ahousing wall.

FIGS. 2, 3 and 4 show in the same sideview, respectively, theprestressing lever and the shift fork behind it, according to thearrangement of FIG. 1, in the possible engaged and disengaged positionsin detail and also the design of the prestressing lever and the shiftfork constructed of sheet metal which reduces the weight and theexpense.

FIGS. 5, 6 and 7 show diagrammatically the three operational states ofthe spring mechanism according to FIGS. 2, 3 and 4.

In FIG. 1 a positive engagement sliding sleeve 2 that is on the drivenshaft 1 is movable in an axial direction by a sliding block 4 located ina peripheral groove 3 of the sliding sleeve 2. The sliding block 4 isrotatably mounted on the pivot end of a shift fork 5, which for its partis pivotably mounted, according to the embodiment, on a pivot shaft 6that crosses the driven shaft 1. The shift fork 5 can be moved in thedirection of rotation about shaft 6, but only via a spring guide 7having a bolt 8 surrounded by a spring 9. The bolt 8, for this purpose,has its end adjacent the shift fork axially moveable in a bolt guide 10disposed on the pivot end of the shift fork 5, in the area of thebearing of the sliding block 4, with its opposite end being moveable onthe pivot end of a prestressing lever 11. Said prestressing lever 11 islimitedly rotatable or pivotable about the pivot shaft 6 which,according to the embodiment, is mounted to a housing wall 12. The pivotlimitations are effected here by a stop pin 15, which starting from thehousing wall 12 reaches into a slot 13 of the stem 14 of theprestressing lever 11, and are determined in a manner such that noengagement of the sliding sleeve 2 is possible until a ball detent 16 isengaged with hole 18 in the prestressing lever. According to theembodiment, the detent 16 consists of a ball 21 which is supported in abore 19 of the housing wall 12 and biased by means of a spring 20 andcan be engaged, when the predetermined angle of rotation is reached, ineither hole 17 or 18 in the stem 14 of the prestressing lever 11 andwhich correspond to the respective engaged or disengaged position.

In FIG. 2 the disengaged position of the mechanism is shown according tothe invention wherein the separation between the drive shaft 22 and thedriven shaft 1 still has not been bridged by the sliding sleeve 22movable thereon. The prestressing lever 11 is here held by the detent 16(not shown in FIGS. 2, 3 or 4), in the hole 17 of the stem 14corresponding to the disengaged position, and the spring 9 of the springguide 7 is at its maximum extension. As a result of a predeterminedresidual initial spring tension, it presses the pivot end of the shiftfork 5 against a side of the sliding sleeve and, on its opposite side,the pivot end of the prestressing lever 11 against the respective ends17A or 18A of the bolt 8, thereby both levers 5, 11 being forced apartfrom one another.

Said levers 5 and 11 are, according to the embodiment, manufactured assheet-metal molded parts that are lightweight and resistant to bending.The shift fork 5 is mounted as a flat stem across the pivot shaft 6 andhas on its pivot end a bolt guide 10 rolled in the manner of a sleevewhile the prestressing lever 11 is designed as an angled section havingits stem 14 parallel with the axis of the shaft, and isprovided with theholes 17, 18 for engagement with the detent 16 and with the slot 13 intowhich the stop pin 15 projects. Through the upper end of the other stemof the prestressing lever 11, parallel with the axis of the pivot shaft,the bolt 8 is inserted, which guides or prestresses the spring 9 betweenthe levers 5, 11 and has an effective length easily changeable at thebolt end 18A by lock nuts situated on the stem side remote from thespring for the purpose of adjusting the spring strength and/or length.

FIG. 3 shows the preselected position for the engaged position of theclutch wherein the sliding sleeve 2 still has not been locked intoengagement with the drive shaft 22, but is already flexibly pressed inthe direction of the drive shaft 22 and against the external splinesthereof via the shift fork 5 by the prestressing lever 11 that has beenpushed into the engaged position and the spring 9 compressed thereby.The compression of the spring 9, thereby shortens the distance betweenthe levers 5, 11. The spring remains compressed with detent 16 engaginghole 18 and results in a two-sided release of the bolt ends 17A or 18Auntil the internal splines of the sliding sleeve 2 can mesh with theexternal splines of the drive shaft 22. Therefore, the driver does nothave to keep his hand on the control lever until the sliding sleeve isengaged, for instance, when engaging an additional drive, but canimmediately bring the operating hand back to the steering wheel.

In FIG. 4 the engaged position has then been completely reached withoutchanging the detent position, while expansion of the spring 9 hasaccomplished a locking engagement of the sliding sleeve 2 with the driveshaft 22. The shift fork 5 and the prestressing lever 11 have, at thesame time, both fully reached their maximum pivot motion limited by thestop pin 15 in regard to the disengaged position. They now again havesubstantially the same separation from each other as shown in FIG. 2,but have rotated about the pivot angle of the pivot shaft 6 axially ofthe drive shaft 22 and the spring 9 is again relaxed to the prestresslength predetermined by the bolt 8 and bolt ends 17A, 18A.

The diagrammatic representation shown in FIG. 5 corresponds to thesituation described and illustrated in FIG. 2, FIG. 6 logicallycorresponds in the same manner to the situation of FIG. 3 and FIG. 7 tothat of FIG. 4.

In FIG. 6, however, the sliding sleeve 2 is shown as having a reduceddiameter, in comparison to FIGS. 5 and 7, to diagramatically depict theabutment of the non-aligned internal and external splines.

With the mechanism according to the invention it is also of specialadvantage from an operational point of view that, on one hand, theengagement can always be easily and quickly possible with the sameactuation resistance but, on the other hand, the return of the slidingsleeve 2 to the disengaged position 18 can be immediately possible,without delay, by a direct springless connection of the pivot lever 6 orprestress lever 11, on one side, and the shift fork 5 on the other viathe bolt 8 abutting on both outer sides on the lever 5, 11 upon thedisengaged movement (see FIG. 2). Thus, the driver receives absolutecertainty that the additional drive is disengaged that is, that thesliding sleeve is positively disengaged. At the same time, the spring iscompressed for only a short time during the actual engagement operationand is thus protected against the danger of fatigue.

By virtue of the fact that the lever stops are here directly integratedin the clutch device itself, remote control such as by linkages can becarried out more easily and operate more reliably. The basic principalof the mechanism according to the invention can naturally beaccomplished also with a larger number of springs/or with separatelever-pivot axes or instead of a pivot arrangement of shift fork andprestressing lever, with switching and prestressing elements rationallymovable linearly with respect to each other.

We claim:
 1. A spring mechanism for a positive engagement clutch havinga sliding sleeve (2) with a peripheral groove (3) thereof engaging witha shift fork (5), for bringing a drive shaft (22) and a driven shaft (1)into and out of locked engagement, and having at least one spring (9)situated outside said sliding sleeve (2) between said shift fork (5) anda prestressing lever (11), characterized in that said prestressing lever(11) has a limited axial movable pivot end connected to a pivot end ofsaid shift fork (5) by a bolt (8) and a locking nut surrounded by saidspring (9), the bolt (8) and the locking nut provide easy adjustment ofa prestressing bias for said spring, a second end of said prestressinglever being pivoted on pivot shaft (6) connected to a housing wall (12)to allow limited axial mobility of the pivot end of said prestressinglever (11), wherein, when said prestressing lever is moved to a driveengaged position said spring (9) initially becomes compressed to bringabout clutch engagement and when moved to a drive disengaged positionsaid spring expands and a rigid connection occurs, by means of said bolt(8) and said locking nut, between said prestressing lever (11) and saidshift fork (5) to positively disengage the drive and driven shafts.
 2. Aspring mechanism according to claim 1, characterized in that when in thedrive engaged position, said spring (9) is compressed to a minimallength by said prestressing lever (11) against said shift fork (5) untilengagement of said sliding sleeve (2) occurs, and said spring (9)expands to a maximum length when in the drive disengaged position andupon engagement of said sliding sleeve (2).
 3. A spring mechanismaccording to claim 1, characterized in that detent means are providedbetween said prestressing lever (11) and the housing wall (12) for thedrive engaged position and the drive disengaged position.
 4. A springmechanism according to claim 1, wherein said pivot shaft (6) is also apivot axis for said shift fork (5).
 5. A spring mechanism according toclaim 1, wherein a shift fork (5) and a prestressing lever (11) areprovided on each side of said sliding sleeve (2) and respective springguide bolts (7) are provided for connection therebetween.
 6. A springmechanism according to claim 1, wherein said detent means comprises astop ball (21) and spring (20) supported in a bore (19) of the housingwall (12) which engage with corresponding holes in a stem (14) of saidprestressing lever (11).